1. Field of the Invention
The present invention relates to a method of creating machining conditions required for machining by a numerically controlled machine tool.
2. Description of the Related Art
An NC (numerical control) automatic programming system is known which, in generating a machining program for a numerically controlled machine tool, automatically computes machining conditions such as a spindle rotational speed and a tool feed speed in accordance with materials of the workpiece and preserves them together with the machining program.
In some conventional NC automatic programming systems in general use, a machining program is not allowed to be generated until all data required for obtaining machining conditions are definitely specified and inputted into the system after the designation of a material of the workpiece. Particularly, in interactive automatic programming systems with a display screen displaying questions to request the operator for an input operation, the subsequent operations are not permitted in the absence of an input operation upon the request to input a material of the workpiece.
In the interactive automatic programming systems, all data necessary for generating a machining program inputted by the operator are converted into a machining program at a time through an operating system. Therefore, all the machining conditions to be finally outputted to a floppy disk or a punch tape for storage include elements associated with the material of the workpiece which has been specified at the stage of interactive data input.
For example, in such a case where the material of the workpiece has to be changed due to design change after the preparation of a machining program has been completed, it is not possible to execute proper machining under the machining conditions determined based on the initial data for the material of the workpiece which has been specified through the data input operation. Thus, it will become necessary for the machining conditions to be modified according to a newly selected material of the workpiece. In order to execute such modification by using the conventional NC automatic programming system or a controller for the NC machine tool, the original data inputted by the operator in creating the machining program has to be invoked once on the display screen of the NC automatic programming system, and, after modifying the part of the program associated with the material of the workpiece, the program is required to be reconverted into an NC data. Alternatively, after invoking the initial machining program on the display screen of the NC machine tool controller to detect commands associated with the spindle rotational speed, the tool feed speed and the like while referring to the screen, new spindle rotational speed, tool feed speed and the like have to be calculated manually for resetting. Thus, the modification associated with the change of material will involve an extremely time-consuming operation.
The same is also true of the case where the initial machining program is directly coded into a punch tape or the like without using the interactive automatic programming system. Thus, the operation for the modification of machining conditions inevitably includes the steps of invoking the initial machining program into the controller of the NC machine tool, detecting commands associated with the spindle rotational speed, tool feed speed and the like while referring to the display screen, and manually calculating new modified values.